Epidermal growth factor (EGF), a polypeptide hormone discovered in the mouse, is also present in man. EGF binds to membranes of epithelial cells to produce anabolic effects and proliferative growth in cultured cells at physiologic concentrations. Human EGF will be purified and an antibody raised. Serum levels of EGF will be measured by radioimmunoassay, competitive membrane receptor binding assay, and a sensitive quantitative biological assay. The possible role of EGF in psoriasis and lamellar ichthyosis, disorders with documented hyperproliferative cytokinetics, will be studied by these assays and in cultured cells from patients with special efforts to look for abnormalities in binding or biological response to EGF. Parallel biochemical studies and quantitative comparison of binding with biochemical effects of EGF following binding will be conducted which would be useful in elucidating any abnormality detected by the screening studies of clinical disorders. Possible membrane or cytoplasmic protein phosphorylation by EGF will be sought. Antagonism by cholera toxin of glucose or amino acid transport, phosphofructokinase activation, or other biochemical effects of EGF will be studied. These studies may help elucidate the mechanisms of the biochemical events preceding mitogenesis by EGF.